The red value means that the author_sort for the book differs from what would be computed using the authors' individual sort values. That happens when you correct the values for a specific book, but not for the author.
See
http://manual.calibre-ebook.com/faq....es-and-sorting for an overview of how calibre deals with names. What that will (or should) explain is that you should change how an author's name is sorted using the Manage Authors dialog. Changing it there will change it in all the books written by that author.